In order to achieve an optical communication system that enables long-distance transmission, it is desirable to increase the power of optical signals as well as reducing transmission loss of the optical fiber, which is a transmission medium, and thereby improving optical signal-to-noise ratio. However, an increase in power of an optical signal causes a deterioration of optical signal-to-noise ratio because of a nonlinear optical effect in the optical fiber. An often used method to address this is to suppress the nonlinear optical effect by increasing the effective core area Aeff of the optical fiber.
However, an increase in effective core area Aeff is associated with a side effect that increases microbending loss. Therefore, in regard to an optical fiber for long-distance transmission, in which loss needs to be kept small when the optical fiber is used in the form of a cable, it is necessary to make some arrangement to prevent or reduce an increase in microbending loss that would be caused by an increase in effective core area Aeff.
Patent Literature 1 discloses a technique to prevent or reduce an increase in microbending loss that would be caused by an increase in effective core area Aeff, by selecting optimal Young's modulus and thickness of a coating layer.